Fingerprinting of the Unsaponifiable Fraction of Vegetable Oils by Using Cryogenically-Modulated Comprehensive Two-Dimensional Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry

The present research is focused on the development of a cryogenically modulated (CM) comprehensive two-dimensional gas chromatography-high resolution time-of-flight mass spectrometry (GC × GC-HR ToFMS) method for the in-depth profiling of the unsaponifiable fraction of vegetable oils. Specifically, twelve vegetable oils (9 extra-virgin olive, soybean, peanut, and hazelnut oils) were subjected to analysis, with particular attention devoted to the higher molecular weight constituents (sterols, vitamin E, triterpenic alcohols). Peak assignment was carried out by using commercial unit-mass MS databases, accurate mass data, literature and on-line freely-available mass spectral information, as well as an in-lab-constructed HR ToFMS lipid database. The main objective of the work was to develop a method to define a well-characterized extra-virgin olive oil fingerprint, to be potentially exploited for vegetable oil differentiation. An additional objective of the investigation was to evaluate the performance of the HR ToFMS system (operated at a mass resolution of 25,000 FWHM) under the challenging analytical conditions of a CM GC × GC-based experiment. The HR ToFMS accurate-mass lipid database was (previously) constructed by acquiring, for the main part, the mass spectra of vegetable oil constituents, well-separated from both the matrix and column bleed background.